Method and system for harvesting micro organisms

ABSTRACT

In an embodiment of the invention, aqueous growth medium in a pond can be used to grow algae which can be pumped to a primary dewatering device where the algae can be separated from the harvested growth media based on the flow of the harvested growth media and gravity. The flow through the primary de-watering device can be optimized to maintain log phase growth in the pond, while minimizing the pumping cost and maximizing the concentration of total solids in the primary de-watered algae.

PRIORITY CLAIM

This application claims priority to the U.S. Provisional Application No.61/354,083, entitled “Method and System for Harvesting Micro Organisms”by Christopher J. Davies et al. filed Jun. 14, 2010. This application isherein expressly incorporated by reference in its entirety.

CROSS REFERENCE TO RELATED APPLICATION

This application is related to the following application: (1) U.S.Utility patent application Ser. No. 11/933,743, entitled “AlgaeProduction” by Ronald A. Erd, filed Nov. 1, 2007 which issued as U.S.Pat. No. 7,905,049, and (2) U.S. Utility patent application Ser. No.:13/020,996, entitled “Algae Production” by Ronal A. Erd, filed Feb. 4,2011. These applications (1)-(2) are herein expressly incorporated byreference in the entireties.

FIELD OF THE INVENTION

This invention relates to a method and system of harvesting microorganisms from a pond.

BACKGROUND OF THE INVENTION

Microalgae can range from approximately 1 μm to greater than 200 μm insize. Some microalgae form chains or colonies of multiple cells. Thecomposition of algae includes lipids, carbohydrates, ribonucleic acidsand proteins. Algae typically require sunlight, water, carbon dioxideand other nutrients in order to grow. The surfaces of algae includenegative charges due to the presence of mannuronic acid, β-L-glucuronicacid, β-D-xylosyl, alginic acid and sulfonated polysaccharide residues.The exact composition of the cell walls varies with algae species andconditions of growth.

Culture of microalgae can be practiced for production of hydrocarbons,synthesis of a source of protein, generation of a number of organicsubstances, wastewater treatment, solar energy conversion andcombinations of the these processes. Nutrient supplements rich in carbondioxide, nitrogen and phosphorous can significantly increase growthrates of algae. Addition of metal ions which generate metal hydroxidescan minimize dispersion forces leading to flocculation. Alternatively,high molecular weight organic polymers can flocculate algae by forming anetwork of bridges. Addition of flocculants into culture medium in orderto induce flocculation is a routine procedure in waste water treatment.

Algae solid-aqueous liquid separation processes include screening,filtration (cake filtration and deep bed filtration), microstrainers,sedimentation, flotation, gravity and centrifugation (fixed wall androtating wall). Wastewater treatment involves the lowering of thesuspended solids to a level acceptable for discharge of the waterwithout causing deleterious effects on the ecology of the dischargearea.

Sedimentation is a physical water treatment process used to settle outsuspended solids in water under the influence of gravity. For example, awater clarifier can be used in the metal finishing industry to removemetal ions from waste water. Alternatively, sedimentation can be used asa primary stage in modern waste water treatment plant, reducing thecontent of suspended solids as well as pollutants embedded in thesuspended solids. Remaining suspended solids can be reduced by chemicalcoagulation and flocculation in subsequent steps.

SUMMARY OF THE INVENTION

In an embodiment of the present invention, a fractionation tank fed by asystem to culture algae can be used to separate the size of algae in amedia to harvest the large cells while returning the smaller less maturesize cells to the system to culture algae to allow further time forgrowth. In this embodiment of the invention, the top primary de-wateredmedia being returned to the system to culture algae is not readilyapparently different from the harvested growth media being fed into thefractionation tank. That is the fractionation tank does not appear to bepurifying or clarifying the harvested growth media even though algaedoes accumulate at the bottom of the fractionation tank. Usingappropriate criteria to regulate the pumping flow rate allows bottomprimary de-watered algae to be harvested from the fractionation tank. Inan embodiment of the present invention, the bottom primary de-wateredalgae can be recovered from the harvested growth media while the aqueousgrowth media can be returned to the pond and encourages the algae tocontinue to grow. In an embodiment of the present invention, a method ofgenerating primary de-watered algae comprises a system to culture algaecontaining aqueous growth media, a primary de-watering device, mans fortransporting the growth media to be harvested to the primary dewateringdevice and a flow control device. The growth media to be harvestedincludes one or more species of algae, wherein the concentration of theone or more species of algae in the system can be used to calculate theharvested growth media concentration. The primary de-watering deviceseparates the harvested growth media into the top primary de-wateredalgae and the bottom primary dewatered algae, wherein the primaryde-watering device includes an entrance for the growth media to beharvested, a first exit for the top primary de-watered algae and asecond exit for the bottom primary de-watered algae. In an alternativeembodiment of the invention, a flow control device regulates the flow ofaqueous growth medium. In an embodiment of the invention, harvestedgrowth media is transported from a system to culture algae into aprimary de-watering device, wherein a flow control device regulates atop primary de-watered algae concentration relative to a growth media tobe harvested concentration between a lower limit of approximately 5% andan upper limit of approximately 75%.

In an embodiment of the present invention, a method is provided for theseparation of algae from growth media to be harvested, the methodcomprising introduction of the growth media to be harvested to afractionation tank comprising an inlet for the growth media to beharvested, an outlet for the top primary de-watered algae, one or moresurfaces to accelerate algae settling, wherein the configuration of theinlet for the growth media to be harvested and the outlet for the topprimary de-watered algae allows for enhanced interaction of theintroduced growth media to be harvested to the one or more surfaces. Inan embodiment of the invention, the method further comprises the removalof bottom primary de-watered algae with minimal disruption of algae thathas settled. In an embodiment of the invention, the method furthercomprises an outlet by which the bottom primary de-watered algae can beremoved. In an embodiment of the invention, the method further comprisesusing the growth media to be harvested from which algae have beenremoved for seeding further algaculture.

In an alternative embodiment of the invention, a flow control deviceregulates the flow of aqueous growth medium. In an embodiment of theinvention, harvested growth media is pumped from the pond into theprimary de-watering device, wherein the flow control device regulatesthe top primary de-watered algae concentration relative to the harvestedgrowth media concentration between a lower limit of approximately 5% andan upper limit of approximately 75%. In another embodiment of theinvention, harvested growth media is pumped from the pond into theprimary de-watering device, wherein the flow control device regulatesthe top primary de-watered algae concentration relative to the harvestedgrowth media concentration between a lower limit of approximately 75%and an upper limit of approximately 95%.

BRIEF DESCRIPTION OF THE DRAWINGS

This invention is described with respect to specific embodimentsthereof. Additional features can be appreciated from the Figures inwhich:

FIG. 1(A) is a flowchart showing the procedure used to optimize growthof one or more selected species of algae in a pond according to anembodiment of the invention;

FIG. 1(B) is a flowchart showing a procedure used to optimize primaryde-watering of growth media to be harvested (GMH) according to anembodiment of the invention;

FIG. 1(C) is a flowchart showing a procedure used to optimize primaryde-watering of growth media to be harvested (GMH) based on the bottomprimary de-watered algae (BPDWA) according to an embodiment of theinvention;

FIG. 1(D) is a flowchart showing a procedure used to optimize primaryde-watering of growth media to be harvested (GMH) based on the ratio ofthe GMH to the pumping cost according to an embodiment of the invention;

FIG. 1(E) is a flowchart showing a procedure used to optimize primaryde-watering of growth media to be harvested (GMH) based on the bottomsecondary de-watered algae (BSDWA) according to an embodiment of theinvention;

FIG. 1(F) is a flowchart showing a procedure used to increase the TOPpump rate as required in the flowcharts shown in FIG. 1(B), FIG. 1(E)and FIG. 1(H) according to various embodiments of the invention;

FIG. 1(G) is a flowchart showing a procedure used to decrease the TOPpump rate as required in the flowcharts shown in FIG. 1(B), FIG. 1(E)and FIG. 1(H) according to various embodiments of the invention;

FIG. 1(H) is a flowchart showing a procedure used to optimize primaryde-watering of growth media to be harvested (GMH) based on the topprimary de-watered algae (TPDWA) according to an embodiment of theinvention;

FIG. 1(J) is a flowchart showing a procedure used to optimize primaryde-watering of growth media to be harvested (GMH) based on the secondaryde-watered algae (SDWA) according to an embodiment of the invention;

FIG. 1(K) is a flowchart showing a procedure used to optimize primaryde-watering of growth media to be harvested (GMH) based on the removalefficiency according to an embodiment of the invention;

FIG. 2(A) is a schematic drawing of the pond, the fractionation tank andthe secondary de-watering device according to an embodiment of theinvention;

FIG. 2(B) is a line drawing of a fractionation tank with double sludgecones used as a primary de-watering device according to an embodiment ofthe invention;

FIG. 2(C) is a line drawing of the sedimentation plates used in afractionation tank according to an embodiment of the invention;

FIG. 3(A) is a flowchart showing the procedure used to optimize growthof one or more selected species of algae in a pond with an in-line PDWDaccording to an embodiment of the invention;

FIG. 3(B) is a flowchart showing a procedure used to optimize primaryde-watering of growth media to be harvested (GMH) with an in-line PDWDaccording to an embodiment of the invention;

FIG. 3(C) is a flowchart showing a procedure used to optimize primaryde-watering of growth media to be harvested (GMH) based on the bottomprimary de-watered algae (BPDWA) with an in-line PDWD according to anembodiment of the invention;

FIG. 3(D) is a flowchart showing a procedure used to optimize primaryde-watering of growth media to be harvested (GMH) based on the ratio ofthe GMH to the pumping cost with an in-line PDWD according to anembodiment of the invention;

FIG. 3(E) is a flowchart showing a procedure used to optimize primaryde-watering of growth media to be harvested (GMH) based on the bottomsecondary de-watered algae (BSDWA) with an in-line PDWD according to anembodiment of the invention;

FIG. 3(F) is a flowchart showing a procedure used to increase the GMHflow with an in-line PDWD as required in the flowcharts shown in FIG.3(B), FIG. 3(E) and FIG. 3(H) according to various embodiments of theinvention;

FIG. 3(G) is a flowchart showing a procedure used to decrease the GMHflow with an in-line PDWD as required in the flowcharts shown in FIG.3(B), FIG. 3(E) and FIG. 3(H) according to various embodiments of theinvention;

FIG. 3(H) is a flowchart showing a procedure used to optimize primaryde-watering of growth media to be harvested (GMH) based on the topprimary de-watered algae (TPDWA) with an in-line PDWD according to anembodiment of the invention;

FIG. 3(J) is a flowchart showing a procedure used to optimize primaryde-watering of growth media to be harvested (GMH) with an in-line PDWDbased on the secondary de-watered algae (SDWA) according to anembodiment of the invention;

FIG. 3(K) is a flowchart showing a procedure used to optimize primaryde-watering of growth media to be harvested (GMH) with an in-line PDWDbased on the removal efficiency according to an embodiment of theinvention;

FIG. 4 shows overhead schematics of (A) a open channel pond with aseparate fractionation tank and (B) an intrachannel fractionation stageaccording to different embodiments of the invention;

FIG. 5 is a schematic of an intrachannel fractionation stage which showsthe fractionation stage uses tubes and plates to separate the algaeaccording to various embodiments of the invention;

FIG. 6 shows an overhead schematic of a carrousel intrachannel clariferwhich can be used in conjunction with an open channel system to separatethe algae according to an embodiment of the invention;

FIG. 7 shows a cross section of a carrousel intrachannel clarifer ofFIG. 6 according to an embodiment of the invention;

FIG. 8 shows (A) a perspective view and (B) a cross section of aside-channel fractionation stage used in an open channel system toseparate the algae according to an embodiment of the invention;

FIG. 9 shows an overhead schematic of an integral fractionation stageused in an intrachannel system to separate the algae according to anembodiment of the invention;

FIG. 10 shows an side view of the integral fractionation stage shown inFIG. 9 according to an embodiment of the invention;

FIG. 11 shows an overhead perspective of a sidewall separator used in anan open channel system to separate the algae according to an embodimentof the invention;

FIG. 12 shows a cut through perspective of a sidewall separator shown inFIG. 11 according to an embodiment of the invention;

FIG. 13 shows an overhead of an integral fractionation stage used in anan open channel system to separate the algae according to an embodimentof the invention;

FIG. 14 shows a cross section of the integral fractionation stage shownin FIG. 13 according to an embodiment of the invention;

FIG. 15 shows an overhead of an integral fractionation stage (only) usedin an an open channel system to separate the algae according to anembodiment of the invention;

FIG. 16 shows a cross section of the integral fractionation stage shownin FIG. 15 according to an embodiment of the invention;

FIG. 17 shows schematically (A) an overhead view of the boatfractionation stage used in an an open channel system to separate thealgae (B) an overhead view of the boat fractionation stage (only) and(C) a cross section of the boat fractionation stage according to anembodiment of the invention;

FIG. 18 shows a vortex fractionation stage used in an an open channelsystem to separate the algae according to an embodiment of theinvention; and

FIG. 19 shows the correlation between the OD measurements and TSmeasurements for dry weight algae.

DETAILED DESCRIPTION OF THE INVENTION

Definitions

The transitional term “comprising” is synonymous with “including,”“containing,” or “characterized by,” is inclusive or open-ended and doesnot exclude additional, unrecited elements or method steps.

The transitional phrase “consisting of” excludes any element, step, oringredient not specified in the claim, but does not exclude additionalcomponents or steps that are unrelated to the invention such asimpurities ordinarily associated with a composition.

The transitional phrase “consisting essentially of” limits the scope ofa claim to the specified materials or steps and those that do notmaterially affect the basic and novel characteristic(s) of the claimedinvention.

As used herein, the terms “fractionation tank” or “fractionation stage”are used to describe a primary de-watering process where less than 75%of the algae in the medium is removed from the medium. Fractionation isdefined as ‘separating into parts based on the density’ and in aspecific embodiment of the invention as ‘separating the algae in themedium based on the density of the algae’.

The term “optical density (OD)” is a measure of the amount of lighttransmitted through a medium in a visible spectrometer at 600 nm. Thismeasure of the concentration of algae in media will vary depending onthe settling time of the algae in the media under the conditions used.Thus using the fractionation tank conditions with different strains ofalgae will give a range of optical densities based on the varyingsettling times of the alge. The term approximately when used before theOD will be used to indicate that the measurement encompasses lower andhigher OD's due to this settling effect. The term “total solids (TS)”refers to the weight of solids recovered after drying the medium. Incontrast to the OD, the TS measurement can be a more absolutemeasurement of the amount of algae in media.

The OD measurements generally correlate well with cell countingestimates of the media, as shown in Table I, where trends observed inthe cell counts are reflected in the OD measurements. It is noted thatbecause the variation in size of algae is not taken into considerationwhen counting the number of cells, it is possible that some of thevariation observed in Table I reflects actual differences between themedia measured using light absorption versus cell counting. The ODmeasurements also correlate well with the TS measurements for dry weightalgae, as shown in FIG. 19.

The term “algae growth medium (AGM)” refers to the medium used to growalgae which can range from 0-4 OD″. The term “primary de-watering device(PDWD)” refers to any process used to increase the concentration of thealgae in the media. The term “growth media to be harvested (GMH)” refersto the AGM after it has entered the PDWD. In various embodiments of theinvention, the GMH ranges from approximately 0.5-4 OD. The term“secondary de-watering device (SDWD)” refers to any process used tofurther increase the concentration of the algae in the media.

TABLE I Comparison of the OD measurements with Cell Count measurementsfor Algae Growth Media (AGM) Days OD (at 600 nm) Cell Counts (×10⁵) 40.65 297 6 0.73 421 6 1.03 656 7 0.92 379 8 0.73 400 8 0.81 241 9 0.92300 10 1.25 593 11 1.12 549

The term “primary de-watered algae medium (PDWA)” refers to the productof the process that fractionates the GMH. The term top PDWA (TPDWA)refers to the medium that is less concentrated than the GMH after thefractionation process of the PDWD. In an embodiment of the invention,the TPDWA is returned to the system used to culture algae. The term“bottom PDWA (BPDWA)” refers to the medium that is more concentratedthan the GMH after the fractionation process of the PDWD. In anembodiment of the invention, the BPDWA can be sent to a secondaryde-watering step.

In some embodiments of the invention that use an intrachannel PDWD thereis little or no difference between the AGM and the GMH at the pointwhere the AGM flows into the PDWD. Even in these cases the term AGM willbe used to identify the inflow into the PDWD whereafter the flow willrefer to GMH until the TPDWA exits the PDWD to return to the openchannel pond as AGM.

The term “bottom SDWA (BSDWA)” refers to the product that is moreconcentrated than the BPDWA after the process of the SDWD. The BSDWA canrange from approximately 10-40% TS. The term “top SDWA (TSDWA)” refersto the medium that is less concentrated than the BSDWA after the processof the SDWD. The TSDWA can be returned to the pond.

The term “log phase growth” refers to the growth phase of algae afterthe initial ‘lag phase’ when the algae are multiplying exponentially bycell division. The term ‘stationary phase’ refers to the phase of algaegrowth after log phase where growth is attenuated, which can be causedby depletion or accumulation of products.

The term “pond” is used to refer to a body of water which can include anocean, a sea, a lake, a river, a stream or a man made structure thatholds a body of water with a volume in excess of 100 m³. The term openpond is used to refer to a pond in direct contact with the atmosphere.

The term ‘biomass recovery’ is used to refer to the amount of BPDWAcollected from the fractionation tank. The biomass recovery is dependenton the rate of flow of the GMH, the concentration of the GMH, the typeof algae, the phase of growth of the algae, and the settlingcharacteristics of the algae.

The term ‘settling time’ is used to indicate the time the GMH is allowedto fractionate in the PDWD which can be calculated based on the flowrate into the PDWD and the volume of the PDWD.

The term ‘flotation characteristics’ refers to the buoyancy of thealgae. The flotation characteristics can depend on a number ofparameters including the species of algae, the growth phase of thealgae, the concentration of algae, the concentration of flocculants inthe growth media, the temperature of the media and the presence andintensity of sunlight.

The term ‘paddle’ refers to a device used to move all or a portion ofthe body of water contained in the pond. A paddle includes a mixer, aturbine, a fan, a wheel, an auger, a pump or other device which caninduce a flow in the AGM in the pond.

The term ‘reseeding’ refers to the addition of less mature microorganism cells to an aqueous growth medium in order to grow the microorganism.

In the following description, various aspects of the present inventionwill be described. However, it will be apparent to those skilled in theart that the present invention may be practiced with only some or allaspects of the present invention. For purposes of explanation, specificnumbers, materials, and configurations are set forth in order to providea thorough understanding of the present invention. However, it will beapparent to one skilled in the art that the present invention may bepracticed without some or all of the specific details. In otherinstances, well-known features are omitted or simplified in order not toobscure the present invention.

Parts of the description will be presented in data processing terms,such as data, selection, retrieval, generation, and so forth, consistentwith the manner commonly employed by those skilled in the art to conveythe substance of their work to others skilled in the art. As is wellunderstood by those skilled in the art, these quantities (data,selection, retrieval, generation) take the form of electrical, magnetic,or optical signals capable of being stored, transferred, combined, andotherwise manipulated through electrical, optical, and/or biologicalcomponents of a processor and its subsystems.

Various operations will be described as multiple discrete steps in turn,in a manner that is most helpful in understanding the present invention;however, the order of description should not be construed as to implythat these operations are necessarily order dependent.

Various embodiments will be illustrated in terms of exemplary classesand/or objects in an object-oriented programming paradigm. It will beapparent to one skilled in the art that the present invention can bepracticed using any number of different classes/objects, not merelythose included here for illustrative purposes.

The invention is illustrated by way of example and not by way oflimitation in the figures of the accompanying drawings in which likereferences indicate similar elements. It should be noted that referencesto ‘an’ or ‘one’ embodiment in this disclosure are not necessarily tothe same embodiment, and such references mean at least one.

The intensity of the negative charge of algal surfaces is a function ofat least the ionic strength of the aqueous algae medium, the pH, thepresence of polysaccharides, the presence of ammonium sulfate, thepresence of auto-flocculants and algae absorption of ions from theaqueous medium. The electro negativity has been shown to increase as thealgae grow. The propensity to flocculate has been attributed to one ormore of the electro negativity of the algae, the counter ions present onthe algae and exuded agents synthesized by the algae. The stability ofaqueous algae medium can depend on a number of parameters including thenegative charge on the algae cell surfaces, the algae cell dimensions,the algae cell density, the nature of counter ions present on the algaecell wall, the ionic strength of the solution, and the presence of analgae exudate. In an embodiment of the invention, metal ions can beadded which generate metal hydroxides which can minimize dispersionforces leading to flocculation of the algae. Alternatively, highmolecular weight organic polymers can flocculate algae through abridging action. In an embodiment of the invention, algal flocculantscan be added into algae cultures in order to induce flocculation. Bothof these means to flocculate algae involve the addition of chemicalswhich can be undesirable for a continuously growing pond and can lead todeleterious or uncontrolled effects on the sustained algae growth.

An important first step in the processing of cultivated algae forcommercial purposes is the separation of the algae from the aqueousmedium in which they are grown. That is, the efficient separationdewatering and drying of microalgae can determine the economicfeasibility of any microalgae production system. This separation anddewatering step is usually achieved by centrifugation. Due to therelatively low concentration of algae in the medium, dewatering bycentrifugation is inefficient and energy intensive. Therefore theexpense can become a prohibitive cost. In an embodiment of theinvention, the method provides a cost efficient means of producingalgae.

Primary De-Watering

In an embodiment of the invention, a method of pre-concentrating thegrowth media to be harvested can be used prior to a secondaryde-watering step. In an embodiment of the invention, a method of primaryde-watering the growth media to be harvested can be used prior to asecondary de-watering step. In an embodiment of the invention, aneffective method of primary de-watering the growth media can use afractionation tank to settle and collect the fractionated algae prior tosecondary de-watering. In an embodiment of the invention, afractionation step can be an energy efficient method of primaryde-watering the growth media to be harvested. In an embodiment of theinvention, a fractionation step can be a cost effective method ofprimary de-watering the growth media to be harvested.

Algae solid-aqueous liquid separation processes include screening,filtration (cake filtration and deep bed filtration), microstrainers,sedimentation, flotation, gravity and centrifugation (fixed wall androtating wall). Screening relies upon passing the aqueous algae mediumthrough a screen of given aperture size. Microstrainers and vibratringscreen filters have been used to separate algae. Filtration relies upona pressure drop for the aqueous algae medium to pass through thefiltrate. The pressure can be applied by gravity, vacuum, pressure andcentrifugal forces. Filtration techniques typically requiresbackflushing to release bound algae. Microstrainers consist of a rotarydrum covered by a straining fabric, stainless steel or polyester. Abackwash spray collects the particles onto an axial trough. Highgradient magnetic filtration has been used for the removal of suspendedparticles and heavy metals from wastewater. In an embodiment of theinvention, gravity sedimentation can separate the aqueous algae mediuminto a slurry of higher concentration and an effluent of substantiallyclear liquid.

Clarifiers can utilize gravity in conjunction with passing the liquidover parallel plates to settle solids from a liquid flow. The liquidinflow can be pre-treated. Next the liquid can be transferred into aflocculation tank where flocculent is added to promote flocculation. Inthe flocculation tank, the liquid can move up through a series of plateswhere the solids can separate out from the liquid and settle to formsludge at the bottom of the clarifier. The clean water can be directedout through laundering troughs for polishing and water reuse or simplyas ‘cleaned’ waste. The solids are typically taken from the sludge conesto be discarded.

The advantage of a clarifier when treating waste water is that theprocess uses gravity and water flow to separate particulate matter.Clarifiers have previously been used to help meet EnvironmentalProtection Agency guidelines and to meet solid discharge requirementsrelating to metal finishing wastes and water municipal wastes.

In an embodiment of the invention, a clarifier tank can be used as afractionation tank. In an embodiment of the invention, a fractionationtank without settling plates can be used to fractionate solids dispersedin a flowing liquid. The rate of flow of the GMH into the fractionationtank equals the rate of flow of TPDWA out through the outlets plus therate of flow of BPDWA out through the outlets. Further, the averageresidence time of the GMH within the fractionation tank is determinedprimarily by the flow rate of GMH into the inlet and the volume of thefractionation tank. In an embodiment of the invention, the sedimentationof the BPDWA from the GMH depends on the chanelling of the GMH enteringthe fractionation tank and the subsequent flow and turbulencecharacteristics of the GMH.

In an embodiment of the invention, TPDWA from which some but not allalgae have been removed can be re-used for algaculture. In an embodimentof the invention, TSDWA from which some but not all algae have beenremoved can be re-used for algaculture. In an embodiment of theinvention, the TPDWA can be recycled back to the open system used toculture algae. In an embodiment of the invention, the TSDWA can berecycled back to the system used to culture algae. In an embodiment ofthe invention, the fractionation tank can utilize gravity in conjunctionwith parallel ‘settling plates’ to settle solids from a liquid flow. Invarious embodiments of the invention, the settling plates can be made ofone or more materials selected from stainless steel, steel, tar coatedsteel, epoxy coated steel, polyethylene, polyester and a non corrosivesubstance. In an embodiment of the invention, the fractionation tank canutilize gravity without settling plates to settle solids dispersed in aflowing liquid.

Measurements made returning the TPDWA to the pond found that not onlywas the TPDWA ideally conditioned with nutrients to grow the selectedspecies of algae, but the TPDWA also carried the correct developmentalstage algae to keep the pond in log phase growth when the GMH was beingpumped at an appropriate rate. It was unexpected that the fractionationtank can return the media to the pond where the algae was sized based onthe absence of settling. It was also unexpected that the returned algaecan be ideal reseeding feedstock for producing further algae in thepond. It was also an unexpected result that an intrachannelfractionation stage can return the TPDWA to the pond where the algae wassized based on the absence of settling. It was also an unexpected resultthat the returned algae can be ideal reseeding feedstock for producingfurther algae in the pond. By eliminating the pumping of AGM to a PDWD,the costs of the algae harvesting can be significantly reduced. However,it was unexpected that the algal growth rates could be increased byusing an intrachannel fractionation stage. The increased growth rateswere attributed to the increased exposure of the TPDWA to seeded mediumand sunlight using an intrachannel fractionation stage as no pumping ofAGM in piping was required. It was noted that while resident in thepiping the AGM is receiving less nutrients, less dissloved carbonatesand less sunlight. The level of nutrients was expected to drop off withthe distance that the AGM was piped from the nutrient source in thepond. The increased growth rates were also attributed to a lesser extentto the reduced handling of the reseeding algae when little or no pumpingin piping was required.

In an embodiment of the invention, the fractionation tank can beoperated at a flow rate too rapid to allow clarification of the GMH butcan act to size fractionate the algae. In an embodiment of theinvention, significant algae can settle at flow rates below 60 GPM. Itwas an unexpected result that the fractionation tank can also be used toaffect a sizing of the algae extracted from the media based on thesettling time for the algae where the residence time of the media in thefractionation tank was less than approximately two hours.

The flow rate through the fractionation tank with return of the TPDWA tothe pond has multiple effects depending on the state of the pond. Afaster flow rate, decreases residence time and thereby nominally removalefficiency (OD reduction from GMH to TPDWA). Nominally, it is expectedthat a fast rate of flow can be utilized to assist the growth of thealgae by returning more algae to the pond and only removing the mostdense or fastest settling algae. Nominally, a slower rate of flow can beused to harvest algae, where all but the less dense or slower settlingalgae can be removed.

However, the mass of the material removed can be dependent on theconcentration and stage of growth of the algae in addition to the rateof the water moving through the fractionation tank. In variousembodiments of the invention, at a flow rate of 10 GPM, the OD of theGMH going to the TPDWA can change from 1.0 to 0.5. Unexpectedly, for thesame pond (i.e., the same concentration, stage of growth and species ofalgae) at a flow rate of 100 GPM, with the OD of the GMH going to theTPDWA can change from 1.0 to 0.8. That is, unexpectedly thefractionation tank can harvest significantly more material at a fasterflow rate. Accordingly, in an embodiment of the invention, as the OD inthe pond increases, the GMH flow rate can be increased. In an embodimentof the invention, a GMH flow rate that is too slow can result in the ODin the pond increasing. This is an unexpected result based on thenominal expectations outlined above. It is counter intuitive that morematerial is removed at the faster flow rate and less material is removedat a slower rate. This observation also reflects the critical balancebetween flow rate and the growth rate of the algae in the pond. It isalso counter intuitive that removal of more material from the GMH allowsmaintenance of the GMH in an appropriate growth rate.

In an embodiment of the invention, the larger and/or denser algae ismore suitable for extracting and refining oil. In an embodiment of theinvention to maximize growth, the pond GMH concentration was held withina desired range and the difference between the GMH and the TPDWA wasadjusted with the flow rate. In this manner, the TPDWA concentrationrelative to the GMH concentration can be initially approximately 5% andthereafter be increased to approximately 75%. At a subsequent time thisratio can vary between 5 and 75%, depending on the condition of thealgae growth in the pond.

In an embodiment of the invention, the aqueous growth medium (AGM) istypically approximately 0-4 OD (optical density). In an embodiment ofthe invention, the growth media to be harvested (GMH) is typicallyapproximately 0.5-4 OD. In an embodiment of the invention, pumping ofthe GMH can begin as soon as the pond has been seeded with the algae. Inthis embodiment, the pumping rate can be very fast (120 GPM or greater)to insure that the algae is not significantly harvested initially. In analternative embodiment of the invention, pumping of the GMH begins whenthe GMH reaches 0.2 OD. In this embodiment, the pumping rate can bereasonably fast (approximately 80 GPM) to insure that the algae is notover harvested initially. In another embodiment of the invention,pumping of the GMH begins when the GMH reaches 0.5 OD. In an embodimentof the invention, an interval of time of approximately seven days can berequired before the concentration of the algae in the AGM has reached asufficient level for harvesting. In an alternative embodiment of theinvention, an interval of time of approximately ten days can be requiredbefore the concentration of the algae in the AGM has reached asufficient level for harvesting. In another embodiment of the invention,an interval of time of approximately fourteen days can be requiredbefore the concentration of the algae in the AGM has reached asufficient level to make harvesting worthwhile. In an embodiment of theinvention, an interval of time of approximately fourteen days afterseeding can be required before log phase growth occurs. In an embodimentof the invention, a fractionation tank can be used to preconcentrategrowth media to be harvested as shown in Table II. Table II shows thatthe primary dewatering step operates with approximately 8-41%efficiency. In various embodiments of the invention, the primaryde-watering can operate with an efficiency of between 10-60%. Afractionation tank can be used to preconcentrate the bottom primaryde-watered algae from the GMH to 0.7-10% TS. In an embodiment of theinvention, further drying can be carried out on the BPDWA. In anembodiment of the invention, after secondary de-watering a BSDWA canyield approximately 10-60% TS.

TABLE II Comparison of GMH and TPDWA Algae Concentrations Growth Mediato be Harvested TPDWA Concentration Concentration Reduction Flow Rate(OD) (OD) in OD (GPM) 0.81 0.69 15 70 0.9 0.7 23 50 0.92 0.85 8 65 1.21.0 17 50 1.2 0.9 25 50 1.2 0.9 25 50 1.7 1.0 41 50

As shown in FIG. 1A, the location, the pond type, the pond size selectedand the specie or species of algae can be selected 100. Nutrients andone or more carboxylate sources such as dissolved CO₂ can then be added105. Based on the species selected, the water temperature can beoptimized 110. The algae growth media (AGM) conditions can be adjustedfor the available sunlight and algae concentration 112. Next the growthmedia to be harvested (GMH) TOP can be pumped to the fractionation tank114. The TPDWA can be returned to the pond 116. Next the TOP pump ratefor the GMH can initially be selected based on the concentration of theAGM 118. In various embodiments of the invention an initial TOP pumprate of 50 GPM can be selected. The TOP pump rate can be optimized tokeep the algae growing in the appropriate phase 120. The BOTTOM pumprate can be adjusted to maximize harvesting 122. The process outlined inFIG. 1A can be optimized according to one or more of the schemes set outin FIGS. 1B-1H and 1J-1K, as shown at 123.

In an embodiment of the invention, shown in FIG. 2A, the AGM from thepond 205 is pumped to the fractionation tank 210. The GMH 222 enters thefractionation tank 210 at inlet 220. The TPDWA 252 exits thefractionation tank at 250 to be returned to the pond 205. The BPDWA 262exits the fractionation tank at 260 and 261 to be sent to one or moresecondary dewatering devices 270. The BSDWA 280 is removed from thesecondary dewatering devices 270. The TSDWA 280 retrieved from thesecondary dewatering devices 270 can either be treated as GMH 222 andfed into the fractionation tank 210 or returned 272 to the pond 205.

As shown in FIG. 2B, the GMH enters the fractionation tank 210 at inlet220. The flow of the media inside the fractionation tank 210 is shown byarrows 230. The media passes downwards towards the bottom of thefractionation tank and is then directed at the sets of inclined plates240. After passing around and/or over the sets of parallel plates 240the medium exits the fractionation tank 210 at 250. The TPDWA exitingthe fractionation tank at 250 near the top of the fractionation tank 210can be returned to the pond 105. Since the process of pumping to thefractionation tank 210 can be a continuous process, the BPDWA can becontinuously removed from the bottom cones 260 and 261. FIG. 2C shows aperspective view of the parallel plates 240.

In an embodiment of the invention, as shown in FIG. 2A a source of heat290 can be used to heat the TPDWA 252 and/or the TSDWA 272 prior toreturn to the pond. In an embodiment of the invention, a source of cold290 can be used to chill the TPDWA 252 and/or the TSDWA 270 prior and/orthe piping used 272 to return to the pond. The heat source 290 cancomprise heat generated by one or more of the following sources: asupply heat source, a recovered heat source, and a waste heat sourcefrom at least one of: a power plant, an industrial process, a cementplant, a kiln, an agricultural product processing plant, a processingplant, an incinerator, a furnace, an oven, an oil refinery, apetrochemical plant, a chemical plant, an ethanol plant, an aminetreating plant, a natural gas processing plant, a steel plant, a metalsplant, an ammonia plant, a coal gasification plant, a refinery, a liquidsynthetic fuel plant, a gas synthetic fuel plant, an industrial plant, amanufacturing plant and a volume of carbon dioxide from a source ofindustrial carbon dioxide emission. The cold source 290 can comprise oneor more of the following sources: a supply cold source, a recovered coldsource, and a waste cold source from at least one of: an industrialprocess, a cement plant, an agricultural product processing plant, aprocessing plant, an oil refinery, a petrochemical plant, a chemicalplant, an ethanol plant, an amine treating plant, a natural gasprocessing plant, a steel plant, a metals plant, an ammonia plant, acoal gasification plant, a refinery, a liquid synthetic fuel plant, agas synthetic fuel plant, an industrial plant, a manufacturing plant anda volume of carbon dioxide from a source of industrial carbon dioxideemission. There are significant cost benefits to introducing theheat/cold through an exchanger 295 as the TPDWA 252 exits thefractionation tank 210. In an embodiment of the invention, the heat/coldexchanger 295 can be used to wrap around the tubing 252 returning theTPDWA to the pond (shell-tube). The liquid passing through thetubing/sleeve can act as a heat/cold exchanger (shell-tube) toheat/chill the tube carrying the GMH 222. In an alternative embodimentof the invention, a liquid—liquid heat/cold exchanger can be used toheat/chill the GMH 222. In various embodiment of the invention, aheat/cold exchanger other than a shell-tube or a liquid—liquid type canbe used to heat/chill the GMH, the TPDWA or the TSDWA. In otherembodiments, any type of heat/cold exchanger can be used. In anembodiment of the invention, the heat exchanger can be positioned toheat the GMH 222 before enterinng the fractionation tank 210. In analternative embodiment of the invention, the heat exchanger can bepositioned after the GMH 222 enters the fractionation tank. In anembodiment of the invention, the heat exchanger can be incorporated intothe settling plates. In an embodiment of the invention, one side of theplates of the fractionation tank can act as heat exchangers to enhancethe removal efficiency. In an embodiment of the invention, the lowerside of the settling plates can be used to heat the GMH 222. In analternative embodiment of the invention, a heat exchanger 295 can beused to heat the TPDWA 252 after it exits the fractionation tank 210 butbefore it enters the pond 205. In this way the heat energy transferredto the media will not interfere with the fractionation process. Further,the heat will be quickly introduced into the pond before it candissipate in the fractionation tank. In an alternative embodiment of theinvention, depending on weather conditions the heat exhanger can be usedto heat the GMH 222 or the TPDWA 252.

The rate of flow of the GMH 222 into the fractionation tank 210 equalsthe rate of flow of the TPDWA 252 out through the outlets 250 plus therate of flow of BPDWA 262 out through the outlets 260 and 261. Theaverage residence time of the GMH within the fractionation tank 210 isprimarily determined by the flow rate of GMH 222 into the inlet 220. Thefractionation tank 210 with and without modifications has previouslybeen used as a clarifier in the metal finishing industry to remove metalions from water. When used as a clarifier to remove metal ions, thespecification flow rate for the clarifier is 120 gallon per minute(GPM). Based on the volume of the fractionation tank, the averageresidence time can be approximately 50 minutes. At a flow rate of 60 GPMthe average residence time of the algae in the fractionation tank 210can be approximately 100 minutes. At a flow rate of 10 GPM the averageresidence time of the algae in the fractionation tank 210 can beapproximately 10 hours.

In an embodiment of the invention, a flow rate of approximately 1-10 GPMresults in significant depletion of the algae from the GMH 222. In anembodiment of the invention, the depletion of the algae from the TPDWA252 being returned to the pond was detrimental to the growth of thealgae in the pond. In an embodiment of the invention, a flow rate ofapproximately 1-10 GPM was unsuitable for sustaining log phase growth.In an embodiment of the invention, by depleting the abundance of theselected algae strain in the TPDWA 252, the selected strain of algaecannot compete against invasive algae species. Although in theory algaewill propogate from a low critical concentration under ideal conditions,when competing against invasive species it can be critical to keep theselected algae strains in log phase growth.

In an embodiment of the invention, a channel system can include afractionation stage to separate algae in the AGM. In an embodiment ofthe invention, an intrachannel fractionation stage can be used as a PDWDto separate algae from the GMH. In an embodiment of the invention, afractionation stage which shares a partition wall with a channel systemcan be used as a PDWD to separate algae from the GMH. In an embodimentof the invention, an intrachannel fractionation stage can be used toseparate the GMH into TPDWA and BPDWA. In an embodiment of theinvention, an intrachannel fractionation stage can be used as a PDWD toseparate algae from the GMH. The rate of flow of the GMH into theintrachannel fractionation stage equals the rate of flow of TPDWA out ofthe PDWD plus the BPDWA transported out of the PDWD. For low rates offlow of the BPDWA, the rate of flow of the GMH into the intrachannelfractionation stage equals the rate of flow of TPDWA of the PDWD.Further, the average residence time of the GMH within the fractionationstage is determined primarily by the flow rate of AGM into the PDWDinlet and the volume of the PDWD. In an embodiment of the invention, thesedimentation of the BPDWA from the GMH depends on the chanelling of theGMH entering the intrachannel fractionation stage and the subsequentflow and turbulence characteristics of the GMH.

FIG. 4 shows overhead schematics of an open channel pond 400 with anintrachannel divider 420 where either (A) a separate fractionation tank415 or (B) an intrachannel fractionation stage 425 (location shown incross hatch shading) according to different embodiments of theinvention. In both FIGS. 4A and 4B, AGM 401 can be added to the openchannel pond 400 and the BPDWA 410, 411 can be transported from the PDWD(415, 425). However, in FIG. 4A the TPDWA is transported 405 back to theopen channel pond 400, whereas in FIG. 4B the GMH flows into the PDWDand the TPDWA exiting the PDWD 425 flows directly back to the openchannel pond 400. In various embodiments of the invention, theintrachannel divider 420 can be located offcenter with respect to themid point between the sides (419, 421) of the open channel pond 400. Anadvantage of an intrachannel fractionation stage or an adjacentfractionation stage is that it is no longer necessary to pump AGM fromthe pond 205 or to return 252 to the pond as shown in FIG. 2A.

FIG. 5 is a schematic of an intrachannel fractionation stage which showsthe pipes 540, baffles 550 and end plates 530, 535 used to separate thealgae, according to various embodiments of the invention. Thefractionation stage can span the entire width of the open ditch channelfrom the intrachannel divider 420 with the end plates 530, 535 forcingthe circulating AGM flow beneath the end plates 530, 535 Baffles 550form the bottom of the fractionation stage. Spaces between the bafflesallow the GMH displaced by the AGM flow to enter the fractionation stageand the TPDWA to return to the open channel. Submerged orifice pipes 540collect the algae and move it from the ditch system.

FIG. 6 shows an overhead schematic of a dual carrousel intrachannelfractionation stage which can be used in conjunction with two adjacentopen channel systems according to an embodiment of the invention. Inletbaffles 658 and inlet control gates 660 control the flow of the AGM asit enters the PDWD. A bridge 656 allows access to the PDWD. Floatingmaterial and/or TPDWA can be removed with launderers 652. A padlle wheel654 regulates the AGM flow and thereby the GMH flow. As shown in FIG. 7the carrousel intrachannel uses a sloped solid floor 764 as a bottomwith the circulating AGM flow forced beneath the solid floor 764. Ineach open channel system, the fractionation stage spans the entire widthof one side of the open channel 421. GMH displaced by the AGM flowenters the front of the fractionation stage through inlet control gates660. Inlet baffles 658 reduce the effects of turbulence at the inlet onfractionation performance. Launders 652 located at the back of thefractionation stage allow floating material including TPDWA to return tothe channel system. BPDWA exits through ports 766 located at the side ofthe sloped bottom.

FIG. 8 shows (A) a perspective view and (B) a cross section of aside-channel fractionation stage used in an open channel systemaccording to an embodiment of the invention. In FIG. 8A the AGM iscirculated with an auger 868 above a horizontal baffle divider 870. Asshown in FIG. 8B, the open channel system consists of a rectangularbasin with a horizontal divider baffle 870 that creates an upper 860 andlower 865 compartments in the channel system. AGM in the open channelsystem continuously circulates, but between the upper 860 and lower 865compartments. Diffusers 872 in the bottom compartment and the auger 868circulate the AGM. Side-channel fractionation stage(s) 874 are builtinto the sides of the open channel system. GMH displaced by the AGM flowenters the slots at the bottom of the fractionation stage 876.Recirculation ports 878 provide for TPDWA to return to the open channelsystem. BPDWA is trapped and transported from the lower compartment.

FIG. 9 shows an overhead schematic of an integral fractionation stageused in an intrachannel system according to an embodiment of theinvention. The circulating AGM enters a funnel 983 where the GMH isseparated and BPDWA flows through a side-tube 876 to a lock 984 (shownin cross hatch shading) defined by barriers 981 and 952. The funnel 983connects to a tube 982, where the side-tube 876 forms a ‘T’. Afterseparation, the tube 982 is used to return the TPDWA past the barrier952. A sipon 980 is located in the lock 984. As shown in FIG. 10 thefractionation stage including the funnel 983 and barrier 985 in thedraft tube 982 are used to transfer TPDWA running underneath the lock984 back into the channel pond. The draft tube 982 creates a headdifferential between the fractionation stage and the channel. This headdifferential permits separated BPDWA to be transferred to the lock 984.Launder(s) 652 within the lock 984 collect and remove floating materialand TPDWA from the lock 984 to the channel system. The siphon 980 isused to collect and transport BPDWA from the channel system.

FIG. 11 shows an overhead perspective of an algae separation processthat uses one or more sidewall separator(s) 1184 in an an open channelsystem. The divider wall 420 in the open channel system is located offcenter such that the flow through 422 plus the combined flow through thesidewall separators 1184 is equivalent to the flow in 418. Each sidewallseparator 1184 projects out from the wall (420, 421) of the open channelsystem and extends its full depth. Most of the circulating AGM flow isthrough 422 between the sidewall separators 1184 while a portion of itenters the inlet 1176. The AGM returns via 418. Inside the sidewallseparator 1184 GMH, enters 1176 and is pushed or displaced by incomingAGM, and moves through inclined baffles 1285 as shown in FIG. 12.Submerged orifice pipes 1240 collect and return the TPDWA to the openchannel system. BPDWA moves down through the baffles 1285 and exits thesidewall separators and the open channel system.

FIG. 13 shows an overhead view of one or more off-axis fractionationstage(s) 1386 used in conjunction with an open channel system accordingto an embodiment of the invention. One or more pipes 1382 used toregulate the AGM flow. One or more channel barriers 1387, 1388 are usedto direct the AGM flow into the fractionation stage(s) 1386. Thefractionation stage(s) can be located adjacent to the open channelsystem and share a divided wall with the outer wall of the open channel(419, 421). As shown in FIG. 14 GMH displaced by the AGM flow enters thefractionation stage through inlet slots 1489 in the common wall 419between the open channel system and the fractionation stage 1386. Oncein the fractionation stage, the flow encounters a baffle 1493 the heightof which can be varied to direct more or less flow through thefractionation stage 1386. One or more launders 1452 at the far side ofthe fractionation stage 1386 can be used to return TPDWA to the channelsystem. TPDWA returns to the open channel system through exit 1494.BPDWA is removed through bottom slots 1490.

FIG. 15 an overhead view of an integral fractionation stage 1586 (only)used in an an open channel system according to an embodiment of theinvention. The fractionation stage 1586 can span the entire side of theopen channel system with standard tube settler modules 1584 locatedacross the entire width from 420 to 421. A barrier 1587 can be used todirect the flow of the AGM into the PDWD which is further defined by theexit wall 1585. As shown in FIG. 16 GMH displaced by the AGM flowproceeds upward through the tube settler modules 1584. TPDWA can bereturned to the open channel system through launderers 1652 at thesurface while BPDWA flows downward through the tube settler modules andcan be removed. Channel flow beneath the fractionation stage 1586 can beincreased by a variable height raised section 1588 on the floor of thechannel.

FIG. 17 shows schematically (A) an overhead view of the boatfractionation stage 1795 used in an an open channel system (B) anoverhead view of the boat fractionation stage 1795 (only) almostspanning the entire width of the open channel 421 and (C) a crosssection of the boat fractionation stage according to an embodiment ofthe invention. As shown in FIG. 17C, the boat fractionation stage isplaced in one side of the open channel system where the circulating AGMflows around and underneath it. GMH, displaced by the inflowing AGM,enters at the downstream end or back of the fractionation stage 1778.GMH enters the front of the fractionation stage over a weir 1797 beforeTPDWA returns to the open channel system. BPDWA exits through returnports that cover the entire bottom of the fractionation stage 1796. Eachport can have its own separate hopper. By design, the boat fractionationstage restricts the flow in the open channel system creating a headdifferential between the fractionation stage and open channel systemthat assists algae removal through the ports.

FIG. 18 shows a vortex fractionation stage used in an an open channelsystem according to an embodiment of the invention. The GMH enters(1888, 1889) the vortex fraction system and a circular motion isimparted on the GMH. This circular motion effects a centrifugal force onthe denser algae particles and combines with the gravitiation force toimpart a downward spiral motion. This enhances the fractionationseparation of the GMH and traps the BPDWA which is collected at thebottom of the vortex fractionator. The TPDWA flows upwards and out 652of the vortex separator returning to the pond.

The BPDWA collected is dictated laregly by the GMH concentration. In anembodiment of the invention, with lower BPDWA concentrations the BPDWAcan be pumped to the secondary dewatering process. With higher BPDWAconcentrations the BPDWA can be too dense to efficiently pump to thesecondary dewatering process. In an embodiment of the invention, withhigher BPDWA concentrations an auger and/or a conveyor can be used totransport the BPDWA to the secondary dewatering process.

In various embodiments of the invention incorporating an intrachannel oradjacent PDWD, a means to control the flow of AGM into the primarydewatering devise can include, a wier, a gate, a cover, a plate, avalve, and a mechanical flow control restrictor.

Intrachannel fractionation stages can restrict the circulating flow ofthe GMH in the channel. The paddles or other flow equipment engineeredto induce the flow in the GMH must overcome these restrictions tomaintain adequate velocities throughout the channel. Designers ofsystems using any of the intrachannel fractionation stages can insurethat the flow adequately mixes the algae feed stock, the AGM, and addedconstituents in the open channel. The flow equipment can be engineeredto overcome the increased headloss in the channel because of the intrachannel fractionation stage.

As shown in FIG. 3A, for an intrachannel fractionation stage located inan open channel pond a number of parameters can be optimized based onthe characteristics of the system including the location, the pond type,the pond size selected and the specie or species of algae selected 300.Nutrients and one or more carboxylate sources such as dissolved CO₂ canthen be added 305. Based on the species selected, the water temperaturecan be optimized 310. The AGM conditions can be adjusted for theavailable sunlight and algae concentration 312. Next the GMH flow can beselected 315. The GMH flow can be optimized to keep the algae growing inthe appropriate phase 320. The BOTTOM pump rate can be adjusted tomaximize harvesting 322. The process outlined in FIG. 3A can beoptimized according to one or more of the schemes set out in FIGS. 3B-3Hand 3J-3K, as shown at 323. In an embodiment of the invention, the TPDWAexiting the intrachannel PDWD is tested before being continuouslyrecycled back to the pond. Based on the concentration of the TPDWAdifferent actions can be taken. In an embodiment of the invention, fromstep 323 a test can be carried out as shown in FIG. 3B, 324. The GMHflow can be decreased 350 (see also FIG. 3G) if the TPDWA concentrationfalls below 0.8 OD 335. Alternatively, the GMH flow can be increased 340(see also FIG. 3F), if the TPDWA concentration increases above 1.8 OD345. After adjusting the GMH flow 340, 350, step 315 is continued at355. Thus, at step 355 the change in GMH flow can be related back to theprocedure shown in FIG. 3A at step 315, and in particular therequirement to keep the algae growing in a particular stage of growth.

In an embodiment of the invention, the GMH flow rate is adjusted to keepthe concentration of the total solids (TS) in a defined range for asecondary dewatering step. FIG. 3(C) is a flowchart showing theprocedure used to optimize primary de-watering of GMH and growth of theTPDWA based on the BPDWA concentration according to an embodiment of theinvention. In FIG. 3(C) the GMH directly enters the fractionation stage.The BPDWA is removed from the fractionation tank using pumping, gravityfeed, an auger or a conveyor. In these embodiment of the invention, fromstep 323 a test can be carried out 324. The BOTTOM transport rate can beincreased 344 if the BPDWA concentration is above 3% TS 336.Alternatively, the BOTTOM transport rate can be decreased 354 if theBPDWA concentration falls below 1% TS 346. After adjusting the BOTTOMtransport rate 344, 354, step 322 is continued at 355. At step 355 thechange in BOTTOM transport rate can be related back to the procedureshown in FIG. 3A at step 322, and in particular the requirement to keepthe algae growing in a particular growth phase.

In an alternative embodiment of the invention, if the BPDWA is greaterthan 5% TS, then the AGM and/or GMH flow can be increased. If the BPDWAis less than 0.7% TS, then the AGM and/or GMH flow can be decreased. Inanother alternative embodiment of the invention, if the BPDWA is greaterthan 10% TS, then the AGM and/or GMH flow can be increased. If the BPDWAis less than 0.2% TS OD, then the AGM and/or GMH flow can be decreased.

In an embodiment of the invention primary de-watering of GMH and growthof the algae can be optimized based on the BPDWA and the cost oftransporting the BPDWA from the pond to the SDWD and the cost oftransporting the TSDWA back into the pond. In FIG. 3(D) the GMH iscontinuously transported from the pond thru the PDWD and the TPDWA iscontinuously returned to the pond. The BPDWA is removed from the PDWDusing pumping, gravity feed, an auger or a conveyor. Based on the ratioof the GMH concentration and the cost of transporting the BPDWA and/orthe cost of transporting the TSDWA different actions can be taken. Forexample, if the GMH concentration/Transport Cost is less than X 337,then the GMH flow can be increased 340 (see also FIG. 3F). If the GMHconcentration/Transport Cost is greater than Y 347, then the GMH flowcan be decreased 350 (see also FIG. 3G). After adjusting the GMH flow340, 350, step 315 is continued at 355. Thus, at step 355 the change inGMH flow is related back to the procedure shown in FIG. 3A at step 315,and in particular the requirement to keep the algae growing in aparticular phase. In an embodiment of the invention, the average costincluding the cost of transporting for the 10-12 days before theintrachannel fractionation stage begins to produce significant amountsof BPDWA can be incorporated into the calculated cost. In an alternativeembodiment of the invention, the average cost excluding the cost oftransporting for the 10-12 days before the intrachannel fractionationstage begins to produce significant amounts of BPDWA can be calculated.In an alternative embodiment of the invention, the size of theintrachannel fractionation stage can be chosen based on the pond size,the transport rate, the settling rate, and/or the removal efficiency. Inanother alternative embodiment of the invention, when the algae are inthe appropriate growth conditions it can take less than 10 days to allowbiomass recovery from the intrachannel fractionation stage.

In an embodiment of the invention, the primary de-watering of GMH basedon the secondary DWA can be optimized according to an embodiment of theinvention. In FIG. 3(E) the BPDWA is transported to a secondaryde-watering device (SDWD) 365. The BPDWA is further concentrated in theSDWD. Based on the total solids in the bottom secondary DWA (BSDWA)generated 370, different actions can be taken. If the BSDWAconcentration is below 10% TS 380, the BOTTOM transport rate can bedecreased 354. After adjusting the BOTTOM transport rate 354, step 322is continued at 355. The change in BOTTOM transport rate can be relatedback to the procedure shown in FIG. 3A at step 322, and in particularthe requirement to keep the algae growing in a particular phase 320.

In FIG. 3F and FIG. 3G the GMH flow can be varied based on the amount ofalgae harvested in either the BPDWA, or the BSDWA, or some compositemeasure involving one of these measures and/or the pumping cost. Aperson having ordinary skill in the art after having read thespecification would understand that the GMH flow and the BOTTOMtransport rate can be independently adjusted to increase or decrease theamount of algae harvested. Similarly, the AGM flow and the BOTTOMtransport rate can be independently adjusted to increase or decrease theamount of algae harvested. Also, the AGM flow and the BOTTOM transportrate can be adjusted in combination to increase or decrease the amountof algae harvested. Finally, the GMH flow and the BOTTOM transport ratecan be adjusted in combination to increase or decrease the amount ofalgae harvested. In FIG. 3F and FIG. 3G the GMH flow and BOTTOMtransport rate can be varied based on the GMH flow or the BOTTOMtransport rate. When removing more solids or more concentrated solidsfrom the BPDWA, a mechanized transport method can be incorporated toassist gravity feeding to the SDWD. In FIG. 3F the GMH flow can beincreased 340 when the GMH concentration is not reduced 342 by anincrease in the GMH flow 340. Alternatively, if the GMH concentration isreduced 342 by an increase in the GMH flow 340 then the BOTTOM transportrate can be increased 346. After adjusting the BOTTOM transport rate346, step 322 is continued at 355. Thus, the change in BOTTOM transportrate can be related back to the procedure shown in FIG. 3A at step 322,and in particular the requirement to keep the algae growing in aparticular phase 320. In FIG. 3G the GMH flow can be decreased 350 whenthe GMH concentration is increased 352 by a decrease in the GMH flow350. Alternatively, if the GMH concentration is increased 352 by adecrease in the GMH flow 350 then the BPDWA can be transferred to a SDWDto generate BSDWA 365. Based on the total solids in the BSDWA generated370, different actions can be taken. If the BSDWA concentration is below10% TS 380, the BOTTOM transport rate can be decreased 354. Afteradjusting the BOTTOM transport rate 354, step 322 is continued at 355.Thus, a decrease in GMH can be related to a change in BOTTOM transportrate which can be related back to the procedure shown in FIG. 3A at step322, and in particular the requirement to keep the algae growing in aparticular phase 320.

In an embodiment of the invention, from step 323 a test can be carriedout as shown in FIG. 3H, 324. If the TPDWA concentration is below 0.8 OD335, the GMH flow can be increased 340. Alternatively, if the TPDWAconcentration is above 1.8 OD 345, the GMH flow can be decreased 350.After adjusting the GMH flow 340, 350, step 315 is continued at 355. Inan embodiment of the invention, from step 323 a test can be carried outas shown in FIG. 3J, 324. The BPDWA can be transported to a secondarydewatering device 365. The BOTTOM transport rate can be increased 344 ifthe BSDWA concentration rises above 30% TS 375 or the BOTTOM transportrate can be decreased 354 if the BSDWA concentration falls below 10% TS380. After adjusting the BOTTOM transport rate 344, 354, step 322 iscontinued at 355.

In an embodiment of the invention, from step 323 a test can be carriedout as shown in FIG. 3K, 324. If the pond efficiency is below U % 338,the GMH flow can be decreased 350. Alternatively, if the pond efficiencyis above V % 348, the GMH flow can be increased 340. After adjusting theGMH flow 340, 350, step 315 is continued at 355. In an embodiment of theinvention, the GMH flow can be decreased when U is set at 10%. In anembodiment of the invention, the GMH flow can be increased when V is setat 70%. In an embodiment of the invention, the pond efficiency (PE) canbe given by PE=(1−([TPDWA]/[GMH]))*100, where [TPDWA] is the TPDWAconcentration in OD and [GMH] is the GMH concentration in OD.

In various embodiments of the invention, one or more of the proceduresshown in FIGS. 3B-3H and 3J-3K can be used to help optimize one or boththe GMH flow and/or the BOTTOM transport rate to maximize the algaeharvest. In various embodiments of the invention, the intrachannelfractionation stage is not used as a water fractionation stage would beused in the water aeration and sludge removal industry. In an embodimentof the invention, the intrachannel fractionation stage is not used aswould be used in the waste water industry.

Example 1

A 620 m² open pond (pond A) with a depth of 25 cm+−5 cm which has avolume of 155 m³ (40,950 gallons, or 155,000 L) is used to grow algae. A932 m² open pond (pond B) with a depth of 25 cm+−5 cm which has a volumeof 155 m³ (40,950 gallons, or 155,000 L) is used to grow algae. Thefractionation tank manufactured by Met-Chem is typically used as part ofa wastewater treatment system for settling metals out of waste waterprior to discharge of the waste water. The fractionation tank isconstructed of carbon steel. In an embodiment of the invention, theinternal plate pack is set at 60 degrees for optimum settling and isconstructed of HDPE plastic. FIG. 2B shows the fractionation tank 210.The Met-Chem 8′ x16′ (10′ height) fractionation tank has a totalcapacity of 1280 cubic feet (9575 gallons, or 36,200 L) and can befilled through a 3 inch inlet 220 with GMH pumped from the AGM grown inthe 620 m² open pond. The open pond is located in Ohio. The GMH can becontinually pumped from the first pond to the fractionation tank (withexceptions for maintenance, operational and service related shutdowns tothe fractionation tank 210) throughout the day and night from March thruto November in Ohio. The GMH can be continually pumped from pond B tothe fractionation tank (with exceptions for maintenance, operational andservice related shutdowns to the fractionation tank 210) throughout theday and night from March thru to November in Ohio. In 2009/2010,shutoffs occurred so that data were obtained from September to November2009 and February to November 2010. The GMH flowed out of thefractionation tank through 3 inch outlets 250. The BPDWA is removedafter settling through second exits 260 and 261. The BPDWA can be pumpedor gravity fed into a secondary de-watering process. The TPDWA exitingthe outlet 250 was returned to the open pond to be re-used foralgaculture.

The concentration of the algae in the media can be measured using aspectrophotometer (Hach DR2700) irradiating a cell (1 cm path length) at600 nm and comparing the absorption of this wavelength with a blank cellof water.

The GMH was circulated through the fractionation tank from the firstpond but no BPDWA was removed until the GMH had reached approximately0.5 OD. In an embodiment, it took approximately 10 days of pumpingthrough the fractionation tank before the GMH in open pond A had reacheda concentration where sufficient BPDWA was collecting in thefractionation tank. Unexpectedly, approximately two (2) to three (3)days after the open pond B had reached log phase growth of the algaepopulation, a critical mass of algae can settle in the fractionationtank. It was the presence of this critical mass of algae in the bottomof the fractionation tank cone that enabled significant harvesting ofalgae. This is exemplified by the fact that the fractionation tank canbe operated within 24 hours when either pond A or B has a critical massof algae and the resulting GMH has greater than 0.5 OD. During theapproximately 10 days prior to establishing the log phase growth, theBPDWA collected was negligable. After the approximately 10 days, theharvesting was between approximately 20 and 150 kg/day (wet weight) anda BPDWA (second) pump (or gravity feed) was required to continuouslyremove the BPDWA from the fractionation tank to a SDWD.

Example 2

A clarifier is typically used to reduce the particulate in waste waterby an order of magnitude or more (e.g., from 100,000 p.p.m. to less than1,000 p.p.m.). By operating a fractionation tank at approximately 50GPM, the efficiency of settling (ES) can be between approximately 5 and25%. In an embodiment of the invention, the ES can be bewteenapproximately 5 and 60% (where ES=(1-([TPDWA]/[GMH]))*100, where [TPDWA]is the TPDWA concentration in OD and [GMH] is the GMH concentration inOD, see Table II above). Unexpectedly, it was found that although theflow rate was too fast to allow complete settling of the algae, theprimary de-watering resulted in an increase in the BPDWA collected.Unexpectedly, the increase in BPDWA outweighed the cost of pumping theGMH through the fractionation tank at the faster rate. Using afractionation tank for settling but not clarification was not known inthe art.

Example 3

In an embodiment of the invention, it was found that using afractionation step can reduce the cost of dewatering the algae. That is,the pumping costs associated with the fractionation tank and the cost ofcentrifuging the PDWA can be significantly less than the cost ofcentrifuging the GMH directly. Using a centrifuge with a capacity of 2GPM can require between 25 and 40 times as many centrifuge hours ofoperation depending on the flow rate of the fractionation tank(operating at 50-80 GPM). Accordingly, a centrifuge acting as the soledewatering means treats bewteen 1/25 and 1/40 of the amount of GMH.Thus, the fractionation tank reduces the amount of water that needs tobe treated with a centrifuge while at the same time reducing the cost ofrunning the centrifuge. This is a significant cost saving. In addition,using a centrifuge allows all of the solids to be recovered, but doesnot allow the return of non-disturbed immature algae cells to the pondfor re-seeding of the pond. Further, the centrifuge does not select fordense algae in the same manner as the fractionation stage. Accordingly,the use of the fractionation tank can offer the ability to (i) selectdense algae for harvesting and (ii) re-seed the pond; advantages overusing a secondary de-watering process such as a centrifuge that wereunexpected.

Example 4

In an embodiment of the invention, the pond can be allowed to go intodifferent phases of growth to allow harvesting of differentcharacteristic algae. In an embodiment allowing the pond to go intostationery phase can be used to increase the lipid content of the algaeharvested. Further, allowing the pond to go into the stationary phasecan enable higher yields as the flow rate is increased and more algaeaccumulate in the pond, an increse in the efficiency of settling in thefractionation pond results. In another embodiment of the invention, thepond can be kept in log phase growth to maximize the biomass growth. Inanother alternative embodiment of the invention, the pond can be kept inlog phase growth to maximize the consumption of carbon dioxide. Inanother alternative embodiment of the invention, the pond can be kept inlog phase growth to increase the trading credits available for theconsumption of carbon dioxide.

Example 5

In an embodiment of the invention, the fractionation tank can beoperated with plates in one side and without plates on the other side.It is estimated that the plated side had approximately 280 sq ft ofsettling area, with 2 inch spacing, while the unplated side had about 44sq ft of settling area, with a distance of nearly 10 feet from top tobottom. Table III shows the yield of algae obtained from a fractionationtank in which one side of the fractionation tank was installed withsettling plates (right side) and the other side did not contain settlingplates (left side). The Bottom Primary De-Watered Algae (BPDWA) obtainedfrom each side of the fractionation tank was separately sent to asecondary de-watering process (centrifugation) and the resulting pelletsweighed. As shown in Table III, it was unexpectedly found that the yieldof algae obtained from the fractionation tank did not correlate with thearea of the settling plates 240 in each side of the fractionation tank(see FIGS. 2B and 2C). In a clarifier the settling plates increase thedownflow of particles in settling and therefore the settling process canbe improved by increasing the area of the settling plates. It was foundthat the overall yield from the side of the fractionation tank withoutthe settling plates installed (Unplated) was lower than the overallyield from the side of the fractionation tank with the settling platesinstalled (Plated). However, it was unexpected that the differencebetween the ‘Unplated’ side and the ‘Plated’ side did not correlate withthe area of the settling plates in each side of the fractionation tank.Thus operating a fractionation tank without settling plates counterintuitively leads to significant settling of algae from the algae growthmedia entering the fractionation tank. While the ratio of sq. ft. ofsettling area was approximately 280:44, the ratio of algae harvested asshown in Table III was approximately 2:1. In the unplated side, thenon-turbulent flow in the downward direction results in significantsettling. Using a clarifier for fractionation of algae, rather thanclarification of wastewater, is not known in the art. Clarifiers clarifytop overflow from watewater. In cointrast, a fractionation stage isreducing the concentration of algae in the top fraction compare dwiththe bottom fraction. Unexpectedly, the separation involves mature cellsbeing concentrated in the bottom fraction and the less mature cellsbeing concentrated in the top fraction allowing the less mature cells tobe easily returned to culture. The advantage of removing the maturecells is not simply confined to increased productivity for theparticular batch being harvested. Similarly the advantage of reseedingthe pond with the less mature cells extends for many reproductive cyclesforward. By removing mature cells, the algae in the pond no longer havethe capability to signals or otherwsie effect a shift from the loggrowth phase to a static growth phase. This allows for the continuousculture of algae for long periods of time. The removal of the maturecells also removes the instrument or a vital component in the mechanismfor slowing down the growth phase. Further, removing the main componentof a clarifier to improve the settling and obtaining significantharvested material is an unexpected result. In an embodiment of theinvention, the fractionation tank can be operated with plates in bothsides. In an alternative embodiment of the invention, the fractionationtank can be operated with no plates in either side. In anotherembodiment of the invention, the fractionation tank can be operated withplates in a portion and no plates in another portion of thefractionation tank.

TABLE III Bottom Secondary De-Watered Algae (BSDWA) obtained from theRight (Plated) compared with the Left (Unplated) Cone of a FractionationTank as a function of the Algae Growth Media (AGM) over a ten (10) dayperiod AGM Concentration Right Cone Left Cone Day (OD) Plated (kg)Unplated (kg) Flow (GPM) 09 0.92 11.953 7.551 50 10 0.98 30.563 14.28420 11 1.1 30.368 14.463 30 12 0.8 24.087 19.560 40 13 0.7 15.147 5.70145 14 0.8 9.960 7.667 50 15 1.0 30.847 21.943 60 16 0.92 44.321 27.79165 17 0.73 54.143 16.045 75 18 0.92 24.919 15.444 60 19 1.3 19.25611.869 60 20 1.1 44.189 10.444 60

Example 6

The introduction of the primary de-watering step which resulted in ahigher concentration of BPDWA was found to increase the performance of anumber of secondary de-watering steps. In an embodiment of theinvention, using centrifugation as the secondary de-watering step,increases the concentration of the BPDWA from approximately 2% toapproximately 15% TS.

Example 7 Covering the Fractionation Tank

It was noticed that algae was floating to the top of the fractionationtank. The floating characteristics were assumed to be at least partiallyinduced by available sunlight. In an embodiement of the invention, inorder to reduce the floating characteristics a cover was placed on thefractionation tank. The cover blocked sunlight and increased the biomassrecovery. When the fractionation tank was covered to limit sunlightavailablity to algae in the fractionation tank, the cover either reducedthe tendancy to float or increased the tendancy of the algae to settle.In an alternative embodiment of the invention, the algae in an uncoveredfractionation tank is harvested at night to reduce the algae flotationcharacteristics.

In an embodiement of the invention, it was noticed that algae settlingcharacteristics increased when a cover was placed on the fractionationtank. A cover can insulate the fractionation tank and thereby keep in orkeep out the heat. A cover can also limit solar heating of thefractionation tank. When the fractionation tank was covered to limitsunlight availablity to algae in the fractionation tank, the coverincreased the settling characteristics of the algae through a thermalmechanism.

In an embodiment of the invention, it was observed that the fastestgrowing pond had less flocculation and settling. However, on cloudy daysthe algae seemed to settle and move more into the water column than onsunny days. In an embodiment of the invention, a cover was placed on thefractionation tank. The cover blocks sunlight which can aid in settlingand the cover can keep in heat. In an embodiment of the invention, aportion of the pond can be covered prior to harvesting to reduce thealgae flotation characteristics or increase the tendancy of the algae tosettle.

Example 8 Adjusting the GMH Pumping Time to Sustain Log Phase Growth

In an embodiment of the invention, the rate of flow is adjusted to keepthe concentration (measured in OD) in the algae pond within a definedrange. In an embodiment of the invention, the size of the pond and/orthe pump rate (see FIGS. 1F and 1G) can be varied to allow thefractionation tank to be run almost continuously (i.e., approximately 24hours per day). In an alternative embodiment the fractionation tank isrun 20 to 24 hours per day. In an alternative embodiment thefractionation tank is run 10 to 20 hours per day. In an embodiment ofthe invention, the TOP pump rate is adjusted to keep the concentration(measured in OD) in the pond within a defined range of log phase growthand the fractionation tank to be run approximately 24 hours per day. Inan embodiment of the invention, the size of the pond is adjusted to keepthe concentration (measured in OD) in the pond within a defined range oflog phase growth and the fractionation tank to be run approximately 24hours per day.

FIGS. 1B-1H and 1J-1J show a series of flowcharts of differentprocedures that can be used to optimize biomass recovery according to avariety of embodiments of the invention. In various embodiments of theinvention, the concentration of one or more parameters selected from thegroup consisting of AGM concentration, GMH concentration, TPDWAconcentration, BPDWA concentration, TSDWA concentration, BSDWAconcentration, AGM condition, GMH condition, TPDWA condition, BPDWAcondition, TSDWA condition, BSDWA condition, TOP pump cost of operation,BOTTOM pump cost of operation, TOP pump capital cost, BOTTOM pumpcapital cost.

In FIG. 1(B) the GMH is passed through the fractionation tank and theTPDWA is continuously recycled back to the pond. Based on theconcentration of the TPDWA different actions can be taken.

In an embodiment of the invention, from step 123 a test can be carriedout as shown in FIG. 1B, 124. The TOP pump rate can be decreased 150(see also FIG. 1G) if the GMH concentration falls below 0.8 OD 135 orthe TOP pump rate can be increased 140 (see also FIG. 1F), if the GMHconcentration increases above 1.8 OD 145. After adjusting the TOP pumprate 140, 150, step 118 is continued at 155. Thus, at step 155 thechange in TOP pump rate can be related back to the procedure shown inFIG. 1A at step 118, and in particular the requirement to keep the algaegrowing in a particular stage of growth.

In an embodiment of the invention, with a GMH concentration of 1.2 OD,the TOP pump rate would only be adjusted if the reduction in OD wasgreater than 20%. This reflects the unexpected discovery thatsignificant amounts of algae can be harvested with only a minimalreduction in the concentration of the algae being pumped through thefractionation tank. The difference between a GMH of 1.2 OD and a TPDWAof 1.0 OD would not be apparent to the untrained human eye. Importantly,as shown in Tables II and III, the 20% reduction in the GMH comparedwith the TPDWA can result in significant biomass recovery.

In this embodiment, a flow rate between 50-70 gallon per minute (GPM)results in considerable concentration of algae present in the aqueousalgae medium exiting through the outflow. In an embodiment of theinvention, the rate of flow is adjusted to keep the concentration of thetotal solids (TS) drawn from the fractionation tank within a definedrange.

In an embodiment of the invention, the GMH flow rate is adjusted to keepthe concentration of the total solids (TS) in a defined range for asecondary dewatering step. FIG. 1(C) is a flowchart showing theprocedure used to optimize primary de-watering of GMH and growth of theAGM based on the BPDWA according to an embodiment of the invention. InFIG. 1(C) the GMH is continuously pumped into the fractionation tank.The BPDWA is removed from the fractionation tank using pumping orgravity feed. In this embodiment of the invention, from step 123 a testcan be carried out 124. The BOTTOM pump rate can be increased 144 if theBPDWA concentration is above 3% TS 136 or the BOTTOM pump rate can bedecreased 154 if the BPDWA concentration falls below 1% TS 146. Afteradjusting the BOTTOM pump rate 144, 154, step 122 is continued at 155.At step 155 the change in BOTTOM pump rate can be related back to theprocedure shown in FIG. 1A at step 122, and in particular therequirement to keep the algae growing in a particular growth phase.

In an alternative embodiment of the invention, if the BPDWA is greaterthan 5% TS, then the TOP pump rate can be increased. If the BPDWA isless than 0.7% TS, then the TOP pump rate can be decreased. In anotheralternative embodiment of the invention, if the BPDWA is greater than10% TS, then the TOP pump rate can be increased. If the BPDWA is lessthan 0.2 OD, then the TOP pump rate can be decreased.

FIG. 1(D) is a flowchart showing the procedure used to optimize primaryde-watering of GMH and growth of the AGM based on the BPDWA and the costof pumping the GMH from the pond thru the fractionation tank and backinto the pond according to an embodiment of the invention. In FIG. 1(D)the GMH is continuously pumped from the pond into the fractionation tankand the TPDWA is continuously returned to the pond. The BPDWA is removedfrom the fractionation tank using pumping or gravity flow. Based on theratio of the GMH concentration and the cost of pumping different actionscan be taken. If the GMH/Pump Cost is less than X 137, then the TOP pumprate can be increased 140 (see also FIG. 1F). If the GMH/Pump Cost isgreater than Y 147, then the TOP pump rate can be decreased 150 (seealso FIG. 1G). After adjusting the TOP pump rate 140, 150, step 118 iscontinued at 155. Thus, at step 155 the change in TOP pump rate isrelated back to the procedure shown in FIG. 1A at step 118, and inparticular the requirement to keep the algae growing in a particularphase. In an embodiment of the invention, the average cost including thecost of pumping for the 10-12 days before the fractionation tank beginsto produce significant amounts of BPDWA can be incorporated into thecalculated cost. In an alternative embodiment of the invention, theaverage cost excluding the cost of pumping for the 10-12 days before thefractionation tank begins to produce significant amounts of BPDWA can becalculated. In an alternative embodiment of the invention, the size ofthe fractionation tank can be chosen based on the pond size, the pumprate, the settling rate, and/or the removal efficiency. In anotheralternative embodiment of the invention, when the algae are in theappropriate growth conditions it can take less than 10 days to allowbiomass recovery from the fractionation tank.

In an embodiment of the invention, FIG. 1(E) is a flowchart showing theprocedure used to optimize primary de-watering of aqueous growth mediumbased on the secondary DWA according to an embodiment of the invention.In FIG. 1(E) the BPDWA is pumped or gravity flowed and loaded into asecondary de-watering device (SDWD) 165. The BPDWA is furtherconcentrated in the SDWD. Based on the total solids in the bottomsecondary DWA (BSDWA) generated 170, different actions can be taken. Ifthe BSDWA concentration is below 10% TS 180, the BOTTOM pump rate orgravity flow can be decreased 154. After adjusting the BOTTOM pump rateor flow rate 154, step 122 is continued at 155. The change in BOTTOMpump rate can be related back to the procedure shown in FIG. 1A at step122, and in particular the requirement to keep the algae growing in aparticular phase 120.

In FIG. 1F and FIG. 1G the TOP pump rate can be varied based on theamount of algae harvested in either the BPDWA, or the BSDWA, or somecomposite measure involving one of these measures and the pumping cost.A person having ordinary skill in the art after having read thespecification would understand that the TOP pump and the BOTTOM pumpand/or BPDWA valve (when the BPDWA is gravity fed to the SDWD) can beindependently or alternatively adjusted in combination to increase ordecrease the amount of algae harvested. In FIG. 1F and FIG. 1G the TOPand BOTTOM pumping rate can be varied based on (i) the TOP pump rate orthe BOTTOM pump rate, (ii) the TOP pump rate or the BPDWA valve apertureand (iii) the TOP pump rate, the BOTTOM pump rate and the BPDWA valveaperture. When removing more solids or more concentrated solids from theBPDWA, a pump can be incorporated to assist gravity feeding to the SDWD.In FIG. 1F the TOP pump rate can be increased 140 when the AGMconcentration is not reduced 142 by an increase in the TOP pump rate140. Alternatively, if the AGM concentration is reduced 142 by anincrease in the TOP pump rate 140 then the BOTTOM pump rate can beincreased 146. After adjusting the BOTTOM pump rate 146, step 122 iscontinued at 155. Thus, the change in BOTTOM pump rate can be relatedback to the procedure shown in FIG. 1A at step 122, and in particularthe requirement to keep the algae growing in a particular phase 120. InFIG. 1G the TOP pump rate can be decreased 150 when the AGMconcentration is increased 152 by a decrease in the TOP pump rate 150.Alternatively, if the AGM concentration is increased 152 by a decreasein the TOP pump rate 150 then the BPDWA can be pumped to transfer to aSDWD to generate BSDWA 165. Based on the total solids in the BSDWAgenerated 170, different actions can be taken. If the BSDWAconcentration is below 10% TS 180, the BOTTOM pump rate or gravity flowcan be decreased 154. After adjusting the BOTTOM pump rate or flow rate154, step 122 is continued at 155. Thus, the change in BOTTOM pump ratecan be related back to the procedure shown in FIG. 1A at step 122, andin particular the requirement to keep the algae growing in a particularphase 120.

In an embodiment of the invention, from step 123 a test can be carriedout as shown in FIG. 1H, 124. If the TPDWA concentration is below 0.8 OD135, the TOP pump rate can be increased 140. Alternatively, if the TPDWAconcentration is above 1.8 OD 145, the TOP pump rate can be decreased150. After adjusting the TOP pump rate 140, 150, step 118 is continuedat 155. In an embodiment of the invention, from step 123 a test can becarried out as shown in FIG. 1J, 124. The BPDWA can be pumped into asecondary dewatering device 165. The BOTTOM pump rate can be increased144 if the BSDWA concentration rises above 30% TS 175 or the BOTTOM pumprate can be decreased 154 if the BSDWA concentration falls below 10% TS180. After adjusting the BOTTOM pump rate 144, 154, step 122 iscontinued at 155.

In an embodiment of the invention, from step 123 a test can be carriedout as shown in FIG. 1K, 124. If the removal efficiency is below U %138, the TOP pump rate can be decreased 150. Alternatively, if theremoval efficiency is above V % 148, the TOP pump rate can be increased140. After adjusting the TOP pump rate 140, 150, step 118 is continuedat 155. In an embodiment of the invention, the TOP pump can be decreasedwhen U is set at 10%. In an embodiment of the invention, the TOP pumpcan be increased when V is set at 70%. In an embodiment of theinvention, the removal efficiency (RE) can be given byRE=(1-([TPDWA]/[GMH]))*100, where [TPDWA] is the TPDWA concentration inOD and [GMH] is the GMH concentration in OD.

In various embodiments of the invention, one or more of the proceduresshown in FIGS. 1B-1H and 1J-1K can be used to help optimize one or boththe TOP pump rate and/or the BOTTOM pump rate to maximize the harvest.In various embodiments of the invention, the fractionation tank is notused as a water clarifier. In various embodiments of the invention, thefractionation tank is not used as a water clarifier would be used in themetal finishing industry. In an embodiment of the invention, thefractionation tank is not used as a typical water clarifier would beused in the waste water industry.

In various embodiments of the invention, the fractionation tank is usedwith faster flow rates than required to allow sufficient settling toclean water in a tank used as a water clarifier. Unexpectedly, it wasfound that by using a faster flow rate the aqueous algae growth mediumin the pond can be kept above a level of 1.0 OD and solids canaccumulate even though the efficiency of settling is relatively low(5-60%).

In an embodiment of the invention, a cover is placed on thefractionation tank to reduce heat loss in the fractionation tank. In anembodiment of the invention, a cover is placed on the fractionation tankto reduce the tendency of the algae to float on or towards the surfaceof the fractionation tank.

The type of fractionation tank that this separation and dewateringmethod uses is known as a clarifier and is used world-wide in sewagetreatment facilities for sludge removal from wastewater. Its use inharvesting algae from mass algaculture has not been previouslydescribed.

In another embodiment, a method is provided for primary de-watering ofalgae from an aqueous growth medium, the method comprising introductionof the aqueous growth medium to a fractionation tank that includes amedium inlet, a medium outlet, one or more surfaces upon which the algaecan settle by gravity and one or more baffles, wherein the configurationof the medium inlet, the medium outlet and the one or more bafflesallows for enhanced exposure of the introduced medium to the one or moresurfaces. In an alternative embodiment of the invention, thefractionation tank further includes an outlet by which the settled algaeconcentrate can be removed, wherein the introduction and removal ofmedium minimally disrupts the algae that has settled out by gravity. Inan embodiment of the invention, the algae concentrate obtained fromprimary dewatering is further de-watered by centrifugation.

Parallel plate fractionation tank. The Met-Chem tank uses gravity inconjunction with the projected settling area of the 60 degree angleparallel plates to settle solids from a pre-treated liquid flow. Whenthe Met-Chem tank is used as a clarifier it meets EPA discharge limitsfor metal finishing wastes. When the Met-Chem tank is used as aclarifier, treated liquid flows first to the flocculation tank wherepolymer is added to promote flocculation growth, and then up through thesettling plates where the solids settle out to the bottom sludge cones.When the Met-Chem tank is used as a clarifier, the clean water flows outthrough special laundering troughs to plant discharge or for polishingfor water reuse. When the Met-Chem tank is used as a clarifier thesolids are intermittently taken from the bottom cone to a filter pressfor further dewatering.

A circular clarifier tank manufactured by Siemens can be used to treatwater or wastewater to remove particles and reduce total solids (TS) tolow levels. The Rim-Flo® center-feed clarifier had an overall hydraulicefficiency of 65%. Effluent suspended solids levels can be maintainedbelow 20 p.p.m. at hydraulic loading up to 1,300 GPD/sq. ft./day.Effluent suspended solids levels below 15 p.p.m. can be achieved atlevels of 800 GPD/sq. ft.

Elimination of the separate secondary clarifier and sludge return systemby using an intrachannel clarifier at first appears to offer manyadvantages. Using any of these devices, however, has severalimplications relative to the design and operation of the facility thatthe designer must consider. The following sections discuss these variousdesign tradeoffs.

A method of fractionating AGM comprises receiving AGM containing one ormore species of algae in an open pond. All or a portion of the AGMcomprising GMH is transferred into a PDWD, wherein the GMH enters thePDWD at a first flow rate. The GMH in the PDWD can be fractionated intoat least a top fraction and a bottom fraction, wherein the PDWDfractionates based on at least the first flow rate and a settling rateof the algae, wherein at least one exit for the top fraction returns topfraction directly to the pond for algaculture and the bottom fraction iscollected.

In various embodiments of the invention, the fractionation tank can beused to harvest cells, where the cells are cells capable of being grownin media. A person having ordinary skill in the art would understand thedifferent nutrient and environment requirements of the cells being grownand modify the protocol accordingly. In various embodiments of theinvention, the fractionation tank can be used to harvest cells, wherethe cells are selected from the group consisting of algae, bacteria,yeast and mammalian cells. In various embodiments of the invention, thefractionation tank can be used to harvest gram negative bacterial cells.In various embodiments of the invention, the fractionation tank can beused to harvest bacterial cells, where the bacterial cells areEscherichia coli.

A method of harvesting algae comprising generating algae at a site;wherein the site includes a pond containing AGM, wherein the AGMincludes one or more species of algae. The site further includes a PDWD,wherein all or a portion of the AGM transported to the PDWD is a GMH,wherein the PDWD fractionates the GMH into at least a top fraction and abottom fraction. The site further includes a paddle for inducing a flowin the AGM, wherein the AGM flow controls a flow rate of the GMHtransported to the PDWD. The site further includes a flow control devicefor adjusting the bottom fraction removed from the PDWD. The methodfurther comprising adjusting one or both the AGM flow and the flowcontrol device to establish a target AGM concentration. The methodfurther comprising stabilizing one or both the AGM flow and the flowcontrol device setting to maintain a fixed AGM concentration. The methodfurther comprising adjusting one or both the AGM flow and the flowcontrol device to establish a target GMH concentration. The methodfurther comprising stabilizing one or both the AGM flow and the flowcontrol device setting to maintain a fixed GMH concentration. The methodfurther comprising adjusting one or both the AGM flow and the flowcontrol device to establish a target TPDWA concentration. The methodfurther comprising stabilizing one or both the AGM flow and the flowcontrol device setting to maintain a fixed TPDWA concentration.

A method of harvesting a micro organism comprising growing the microorganism at a site; wherein the site includes a vessel containing AGM,wherein the AGM includes the one or more species of micro organisms. Thesite further includes a PDWD, wherein all or a portion of the AGMtransported to the PDWD is a GMH, wherein the PDWD fractionates the GMHinto at least a top fraction and a bottom fraction. The site furtherincludes a paddle for inducing a flow in the AGM, wherein the AGM flowcontrols a flow rate of the GMH transported to the PDWD. The sitefurther includes a flow control device for adjusting the bottom fractionremoved from the PDWD. The method further comprising adjusting one orboth the AGM flow and the flow control device to establish a target AGMconcentration. The method further comprising stabilizing one or both theAGM flow and the flow control device setting to maintain a fixed AGMconcentration. The method further comprising adjusting one or both theAGM flow and the flow control device to establish a target GMHconcentration. The method further comprising stabilizing one or both theAGM flow and the flow control device setting to maintain a fixed GMHconcentration. The method further comprising adjusting one or both theAGM flow and the flow control device to establish a target TPDWAconcentration. The method further comprising stabilizing one or both theAGM flow and the flow control device setting to maintain a fixed TPDWAconcentration.

A method of fractionating algae grown in media comprising receiving AGMcontaining one or more species of algae in a PDWD, wherein the GMHenters the PDWD at a first flow rate and fractionating the GMH in thePDWD into at least a top fraction and a bottom fraction, wherein thePDWD fractionates based on at least the first flow rate and a settlingtime, wherein at least one exit for the top fraction is directed toalgaculture. The method further comprising collecting the bottomfraction so as to reduce the ability of the mature cells to slow downgrowth in the top fraction directed for further algaculture.

While the present invention has been described in some detail forpurposes of clarity and understanding, one skilled in the art willappreciate that various changes in form and detail can be made withoutdeparting from the true scope of the invention. All figures, tables, andappendices, as well as patents, applications, and publications, referredto above, are hereby incorporated by reference.

Embodiments of the present invention can include providing code forimplementing processes of the present invention. The providing caninclude providing code to a user in any manner. For example, theproviding can include transmitting digital signals containing the codeto a user; providing the code on a physical media to a user; or anyother method of making the code available.

Embodiments of the present invention can include a computer-implementedmethod for transmitting the code which can be executed at a computer toperform any of the processes of embodiments of the present invention.The transmitting can include transfer through any portion of a network,such as the Internet; through wires, the atmosphere or space; or anyother type of transmission. The transmitting can include initiating atransmission of code; or causing the code to pass into any region orcountry from another region or country. A transmission to a user caninclude any transmission received by the user in any region or country,regardless of the location from which the transmission is sent.

The foregoing description of embodiments of the methods, systems, andcomponents of the present invention has been provided for the purposesof illustration and description. It is not intended to be exhaustive orto limit the invention to the precise forms disclosed. Manymodifications and variations will be apparent to one of ordinary skillin the relevant arts. For example, steps performed in the embodiments ofthe invention disclosed can be performed in alternate orders, certainsteps can be omitted, and additional steps can be added. The embodimentswere chosen and described in order to best explain the principles of theinvention and its practical application, thereby enabling others skilledin the art to understand the invention for various embodiments and withvarious modifications that are suited to the particular usedcontemplated. Other embodiments are possible and are covered by theinvention. Such embodiments will be apparent to persons skilled in therelevant art(s) based on the teachings contained herein. The breadth andscope of the present invention should not be limited by any of theabove-described exemplary embodiments, but should be defined only inaccordance with the following claims and their equivalents.

What is claimed is:
 1. A method of cultivating and harvesting algaecomprising the steps of: (a) generating one or more species of algae ata site by seeding a pond containing aqueous growth medium (AGM); (b)connecting the pond to a primary de-watering device (PDWD) including oneor more baffles, one or more inlets and a plurality of outlets, whereall or a portion of the AGM introduced to the PDWD through the one ormore inlets is a growth media to be harvested (GMH); (c) fractionatingthe GMH into at least a top fraction and a bottom fraction during asettling time; (d) adjusting a flow control device adapted to remove thebottom fraction from the PDWD through at least one of the plurality ofoutlets of the PDWD; (e) removing the bottom fraction through at leastone of the plurality of outlets of the PDWD so that the concentration ofalgae in the top fraction is lower than the concentration of algae inthe GMH; and (f) returning the top fraction to the pond through one ormore of the plurality of outlets of the PDWD.
 2. The method of claim 1,further comprising heating the top fraction using a heat exchangerlocated in the PDWD.
 3. The method of claim 1, where waste heat is usedto heat the top fraction.
 4. The method of claim 1, further comprisingheating the GMH entering the PDWD using a heat exchanger located in thePDWD.
 5. The method of claim 4, where waste heat is used to heat theGMH.
 6. The method of claim 1, further comprising heating the GMH usinga heat exchanger located in the pond.
 7. The method of claim 6, wherewaste heat is used to heat the GMH.
 8. The method of claim 1, where oneor both the flow rate and the flow control device are adjusted so thatthe concentration of algae in the top fraction returned to the pond isbetween: a lower limit of approximately 5 percent; and an upper limit ofapproximately 60 percent of the concentration of algae in the GMH. 9.The method of claim 8, where waste heat is used to heat the top fractionexiting the PDWD to return to the pond.
 10. The method of claim 1, wherethe flow rate is set to maintain the concentration of algae in the topfraction returned to the pond between: a lower limit of approximately0.5 Optical Density; and an upper limit of approximately 2 OpticalDensity.
 11. The method of claim 1, where the flow rate is set tomaintain the AGM concentration between: a lower limit of approximately0.5 Optical Density; and an upper limit of approximately 2 OpticalDensity.
 12. The method of claim 1, where the PDWD fractionates the GMHinto at least a top fraction and a bottom fraction based on one or bothsize and density of at least one of the one or more species of algae.13. The method of claim 1, where the settling time is between: a lowerlimit of approximately 30 minutes; and an upper limit of approximately120 minutes.
 14. The method of claim 1, where the flow rate is set tomaintain the concentration of algae in the bottom fraction removed fromthe PDWD between: a lower limit of approximately 1% Total Solids; and anupper limit of approximately 5% Total Solids.
 15. The method of claim 1,further comprising one or both concomitant with and after removaltransporting the bottom fraction to a secondary de-watering device at atransport rate, where the transport rate is adjusted to maintain theconcentration of algae in the bottom fraction removed from the PDWDbetween: a lower limit of approximately 0.5% Total Solids; and an upperlimit of approximately 5% Total Solids.
 16. The method of claim 1,further comprising transporting the bottom fraction to a secondaryde-watering device at a transport rate, where the transport rate isadjusted to maintain the concentration of algae in the bottom fractionremoved from the PDWD between: a lower limit of approximately 3% TotalSolids; and an upper limit of approximately 10% Total Solids.
 17. Themethod of claim 1, where the GMH is transferred to the PDWD continuouslytwenty four hours a day.
 18. The method of claim 1, where the PDWD is anintrachannel fractionation stage.
 19. The method of claim 18, where thePDWD is selected from the group consisting of a boat fractionationstage, a vortex fractionation stage, a sidewall separator fractionationstage, a sidechannel fractionation stage and an integral fractionationstage.
 20. A method of cultivating and harvesting algae comprising: (a)generating one or more species of algae at a site by seeding a pondcontaining aqueous growth medium (AGM); (b) connecting the pond to aprimary de-watering device (PDWD) including one or more tubes connectedto a heat exchanger, an inlet and an outlet, where all or a portion ofthe AGM introduced to the PDWD through the inlet is a growth media to beharvested (GMH); (c) fractionating the GMH into at least a top fractionand a bottom fraction; (d) adjusting a flow control device adapted toremove the bottom fraction from the PDWD through the outlet; (e)collecting the bottom fraction removed through the outlet of the PDWD sothat the concentration of algae in the top fraction is lower than theconcentration of algae in the GMH; (f) returning the top fraction to thepond to seed the pond in step (a); and (g) heating the top fractionreturned to the pond through the one or more tubes.
 21. A method ofcultivating and harvesting algae comprising: (a) generating one or morespecies of algae at a site by seeding an open pond containing aqueousgrowth medium (AGM); (b) connecting the pond to a primary de-wateringdevice (PDWD) including one or more baffles connected to a coldexchanger, an inlet and an outlet, where all or a portion of the AGMintroduced to the PDWD through the inlet is a growth media to beharvested (GMH); (c) fractionating the GMH into at least a top fractionand a bottom fraction; (d) adjusting a flow control device adapted toremove the bottom fraction from the PDWD through the outlet; (e) coolingthe bottom fraction through the one or more baffles; (f) collecting thebottom fraction removed through the outlet of the PDWD so that theconcentration of algae in the top fraction is lower than theconcentration of algae in the GMH; and (g) returning the top fraction tothe pond through the outlet of the PDWD.